This invention relates generally to magnetic disc drives, and more particularly, to a method and apparatus for preventing contamination of a magnetic disc by particles outgassed from a central bearing assembly upon which the disc is mounted for rotation.
As is well known in the art of magnetic disc information storage and retrieval systems, it is essential that the disc or discs upon which information is to be stored are kept as clean as possible to avoid interference with the read/write heads which must operate in very close proximity to the surface of the disc. Toward this end, air is ordinarily circulated inside the compartment containing the rotating magnetic disc and caused to pass through a filter to constantly remove small particles from the air within the compartment. Although filtration of the air surrounding the disc helps to maintain the clean atmosphere required for reliable operation of a magnetic disc, minute particles, generally of lubricants, will occasionally outgas from the central bearing or bearings upon which the disc is mounted for rotation. If these particles, or any other particles within the bearing chamber, are permitted to migrate onto a surface of the magnetic disc, interference with the reliable operation of the information storage and retrieval system is likely to result.
In order to inhibit the outgassing of particles from the central rotary bearings, hermetically sealed bearings are ordinarily employed, but even these bearings are capable of outgassing a sufficient quantity of contaminants to interfere with operation of the information storage and retrieval system. Accordingly, attempts have been made to overcome this problem by interposing a labyrinthine passage between the bearing nearest the magnetic disc compartment and the compartment itself. While this arrangement serves to slow the migration of outgassed particles from the bearing to the disc compartment, some contamination of the disc may still occur after the system has operated for a sufficient period of time.
This problem is particularly troublesome in an information storage and retrieval system in which the magnetic disc compartment is sealed and the disc, or group of discs, is intended to be non-removable. In such a system, it is very important that no contaminating particles are permitted to enter the disc compartment for the entire useful life of the disc drive mechanism.
Accordingly, there exists a need for a convenient and effective method and apparatus for preventing the contamination of a rotating magnetic disc by particles outgassed from the central bearing upon which the disc is mounted for rotation. As will become apparent from the following, the present invention satisfies that need.